1. Field of the Invention
This invention relates generally to pipe joints having flexible fluid-type seals.
2. Description of Related Art
Storm and sanitary sewer pipes are generally made of plastic, metal, concrete, or other suitable materials fabricated in configurations and sizes to meet particular requirements or specifications. It is known in the art to form grooves or provide recesses in ribbed or corrugated types of pipe. Spigots (i.e., male pipe sections) are the dominant method performed for manufacturing sewer pipe, although grooves can be formed in bells (i.e., female pipe sections). Resilient seals are typically provided by polymeric gasket elements. O-ring type gaskets are one type of resilient seal that is frequently employed. An O-ring can be mounted on the spigot and then the spigot pushed into the bell.
It is known in the art that O-rings may distort non-uniformly, resulting in weak seals or voids through which liquids can flow. Thus, spigots are often provided with a circumferential groove or a single or double offset shoulder to keep the O-ring from rolling as the pipes are interconnected. Nevertheless, if the diameter of the O-ring and its radial cross-section are greater than the depth of the groove or shoulder, the ring may still roll over the inside edge of the groove, become snagged, or shear off segments of the O-ring as the spigot enters the bell. Various gasket profiles have been used or suggested to overcome these deficiencies.
One conventional pipe joint has an outer pipe and an inner pipe inserted into the outer pipe wherein one of the outer and inner pipe comprises an annular groove. A gasket is positioned within the annular groove and is adapted to provide a seal between the outer pipe and the inner pipe. The gasket comprises an annular gasket body of resilient material. A protrusion extending radially away from the gasket body is located on the gasket body and is bisected by a centerline thereof. An annular bore extends through in the gasket body. The gasket is used between a first pipe and a second pipe, and is placed with its body essentially filling a U-shaped groove in one of the pipes. A number of compression points are provided that are in contact with respective surfaces of the first pipe and the second pipe, including surfaces of the groove. When compressed, a sealing contact is established between a first compression point and an inner surface of the pipe not having the groove, and sealing contacts are established via contact of several additional compression points with the walls of the groove. Thus, except for a small aperture through the base of the gasket, it is the case both before and after compression that the gasket essentially completely fills a groove in one of the pipes.
In view of the large number of pipe joints that may be installed in a typical sewer system, conventional gaskets require more gasket material then is economical. In addition, because their requires them to essentially fill a groove to function properly, such gaskets are impracticable for use in pipe joints in which suitable grooves are not provided.